Evanescent wave excitation of palladium metalated porphyrins as self-assembled monolayers and phosphorescence quenching by oxygen

The novel palladium metalated derivatives of 5,5'-[8,8'-di(thiooctyloxy)-4,4'-phenyl)]-10,10',15,15',20,20'-hexakis(4,4'-t-butylphenyl)diporphyrin and 5,5'-[8,8'-di(thiooctyloxy)-4,4'-phenyl)]10,10', 15,15', 20,20'-hexakis(3,3',4,4',5,5'-hexakisdecyloxyphenyl)diporphyrin, 1 and 2 respectively, have been synthesized and deposited to form self-assembled monolayer (SAM) films on gold-coated glass slides that served as substrates. The SAM films have been characterised by RAIR spectroscopy. Excitation of the molecules within the films has been achieved using the evanescent field arising when the glass substrate was used as a waveguide. Luminescence spectroscopy detected both fluorescence and phosphorescence emission from the SAM films under an argon atmosphere. Quenching of the phosphorescence emission by dioxygen was investigated for both films. Greater reproducibility of data was achieved from the SAM films of compound 2. The phosphorescence quenching from these films followed the Stern-Volmer relationship.